function dosth(){
    return true;
}

function async(failure,success){
    if(dosth()){
        success();
    }else{
        failure();
    }
}

async(
    function(){console.log(" handle failure")},
    function(){console.log("handle success")}
);

/*
*
* Node's built-in modules often utilize callbacks with two arguments,
* one for error,one for results.
* eq:
* var fs = require("fs");
* fs.readFile("XXX",function(error,content){xxxx});
*
* */